The present invention relates to compounds in which a transition metal is complexed with two xcfx80 systems. particularly with aromatic xcfx80 systems (metallocenes), and the two systems are reversibly joined to each other by at least one bridge comprising a donor and an acceptor, wherein at least one of the donor or acceptor atoms is part of the associated xcfx80 system in each case. The coordinate bond which is formed between the donor atom and the acceptor atom produces a positive (partial) charge on the donor group and produces a negative (partial) charge on the acceptor group: 
The present invention further relates to the use of these new xcfx80-complex compounds, particularly of new metallocenes. as polymerisation catalysts.
Metallocenes have long been known as xcfx80-complex compounds, as has their use in the polymerisation of olefines (EP-A 129 368 and the literature cited therein). Furthermore, it is known from EP-A 129 368 that metallocenes, in combination with aluminium alkyl/water systems as co-catalysts, constitute effective systems for the polymerisation of ethylene (thus, for example, methylaluminoxane=MAO is formed from about 1 mole of trimethylaluminium and 1 mole of water. Other stoichiometric ratios have also been successfully used (WO 94/20506)). Moreover, metallocenes are already known which comprise cyclopentadienyl skeletons which are covalently linked to each other by a bridge. As an example of the numerous patents and patent applications in this field, EP-A 704 461 should be mentioned, wherein the linking group cited therein constitutes a (substituted) methylene group or ethylene group, a silylene group, a substituted silylene group, a substituted germylene group or a substituted phosphine group. In EP-A 704 461, bridged metallocenes are also provided as polymerisation catalysts for olefines. Despite the numerous patents and patent applications in the field, there is a continuing desire for improved catalysts which are distinguished by a high activity, so that the amount of catalyst remaining in the polymer is small, and which at the same time are suitable for the polymerisation and copolymerisation of olefines to form thermoplastics and to form elastomeric products, and which are also suitable for the polymerisation and copolymerisation of diolefines optionally with olefines.
It has now been found that particularly advantageous catalysts can be produced which comprise bridged xcfx80-complex compounds. particularly metallocene compounds, in which the bridge between the two xcfx80 systems is produced by one, two or three reversible donor-acceptor bonds, and in which a coordinate bond or what is termed a dative bond is formed in each case between the donor atom and the acceptor atom, on which coordinate bond an ionic bond is superimposed, at least formally, and in which at least one of the donor or acceptor atoms is part of the associated xcfx80 system in each case. In addition to the bridged state denoted by the arrow between D and A, the reversibility of the donor-acceptor bond also permits the unbridged state, in which, as a result of the rotational energy inherent in them, the two xcfx80 systems can rotate in relation to each other, by 360 degrees of angle for example, without the integrity of the metal complex being lost. After a complete rotation, the donor-acceptor bond xe2x80x9csnaps inxe2x80x9d again. In the presence of a plurality of donors and/or acceptors, a xe2x80x9csnapping-inxe2x80x9d process such as this can even occur after less than 360 degrees of angle have been traversed. Metallocenes according to the present invention can therefore only be represented by a double arrow, and partial formulae (Ia) and (Ib) represent the inclusion of both these states.
Accordingly, the present invention relates to xcfx80 complex compounds. and particularly metallocene compounds of formula 
wherein
xcfx80I and xcfx80II represent xcfx80 systems which bear charges which are different from each other or which are electrically neutral, and which can be singly- or doubly-condensed with unsaturated or saturated five- or six-membered rings,
D denotes a donor atom which is a substituent of xcfx80I or is part of the xcfx80 system of xcfx80I, and which has at least one free electron pair available in its respective bonding state,
A denotes an acceptor atom which is a substituent of xcfx80II or is part of the xcfx80 system of xcfx80II, and which has an electron pair vacancy in its respective bonding state,
wherein D and A are linked by a reversible coordinate bond in such a way that the donor group assumes a positive (partial) charge and the acceptor group assumes a negative (partial) charge, and wherein at least one of D and A is part of the associated xcfx80 system in each case,
wherein D and A themselves may comprise substituents,
wherein each xcfx80 system or each condensed-on ring system can contain one or more D or A entities, or D and A entities, and
wherein in xcfx80I and xcfx80II, in the non-condensed or in the condensed form, one to all of the H atoms of the xcfx80 system, independently of each other, can be substituted by identical or different radicals from the group comprising a linear or branched C1-C20 alkyl which can be substituted singly to completely by halogens, can be substituted singly to three-fold by phenyl or can be substituted singly to three-fold by vinyl; a C6-C12 aryl, and a halogenoaryl comprising 6 to 12 C atoms; and said H atoms can also be singly- or doubly-substituted by D and A, so that the reversible coordinate Dxe2x86x92A bond is formed (i) between D and A, which both constitute parts of the respective xcfx80 system, or (ii) from the D or A part of the xcfx80 system and the other substituent of the non-condensed xcfx80 system or of the condensed-on ring system in each case, or (iii) both D and A are such substituents, wherein in the case of (iii) at least one additional D or A entity or both is (are) part of the xcfx80 system or of the condensed-on ring system,
M represents a transition metal of subgroups III, IV, V or VI of the periodic table of the elements (Mendeleev), including the lanthanides and actinides,
X denotes an anion equivalent, and
n denotes the numbers zero, one, two, three or four depending on the charge of M and on those of xcfx80 and xcfx80II.
In FIG. 1, the structure of dimethylboranyl-cyclopentadienyl-tetramethylphospholyl-titanium tetrachloride is illustrated as an example (see the Examples).
xcfx80 systems according to the invention comprise substituted and unsubstituted ethylene, allyl, pentadienyl, benzyl, butadiene, benzene, the cyclopentadienyl anion, and species which are formed by the replacement of at least one C atom by a hetero atom. Of the aforementioned species, cyclic species are preferred. The type of coordination of ligands (xcfx80 systems) such as these to the metal can be of the "sgr" type or of the xcfx80 type.
xcfx80-complex compounds of formula (I) in which the xcfx80 systems are cyclic and aromatic (metallocenes), can be prepared, for example, either by the reaction of a compound each of formulae (II) and (III) 
or by the reaction of a compound each of formulae (IV) and (V) 
or by the reaction of a compound each of formulae (VI) and (VII) 
with the separation of Mxe2x80x2X in the presence or absence of an aprotic solvent, or by the reaction of a compound each of formulae (VIII) and (III) 
or by the reaction of a compound each of formulae (IV) and (IX) 
or by the reaction of a compound each of formulae (X) and (VII) 
with the separation of E(R1R2R3)X and F(R4R5R6)X in the absence or presence of an aprotic solvent, wherein
xcfx80I, xcfx80II, D, A M, X and n have the meanings given above,
xcfx80III and xcfx80IV represent two different uncharged xcfx80 systems with a structure corresponding to xcfx80I or xcfx80II,
Mxe2x80x2 denotes a cation equivalent of an alkali or alkaline earth metal or Tl,
E and F, independently of each other, denote one of the elements Si, Ge or Sn, and
R1, R2, R3, R4, R5 and R6, independently of each other, represent a straight chain or branched C1-C20 alkyl or C6-C12 aryl, or a C1-C6 alkyl-C6-C12 aryl, a C6-C12 aryl-C1-C6alkyl, vinyl, allyl or a halogen,
wherein, moreover, in formulae (VIII), (IX) and (X), hydrogen can be present instead of E(R1R2R3) and F(R4R5R6), X can also represent an amide anion of the R2Nxcex8 type or a carbanion of the R3Cxcex8 type, or an alcoholate anion of the ROxcex8 type, and wherein it is possible in addition to react compounds of formulae (II) or (VIII) in the presence of compounds of formulae (V) or (IX) directly with a transition metal compound of formula (VII), Furthermore, two X anions can be joined to form a dianion, optionally with a single- or multi-atom bridge interposed therebetween.
In the last-mentioned variant of the reaction of (VIII) with (III) or of (IV) with (IX) or of (X) with (VII), structure (I) is formed with the separation of an amine R2NH or R2NE(R1R2R3) or R2NF(R4R5R6) or of a hydrocarbon compound of formula R3CH or R3CE(R1R2R3) or R3CF(R4R5R6) or of an ether ROE(R1R2R3) or ROF(R4R5R6), wherein the organic radicals R are identical to or different from each other and, independently of each other, represent a C1-C20 alkyl, a C6-C12 aryl, or a substituted or unsubstituted allyl, benzyl, or hydrogen. Examples of the amine, ether, hydrocarbon, silane, stannane or germane which is separated include dimethylamine, diethylamine, di-(n-propyl)-amine, di-(isopropyl)-amine, di-(tertiary-butyl)-amine, tertiary butylamine, cyclohexylamine, aniline, methyl-phenyl-amine, di-(allyl)-amine or methane, and toluene, xylene, trimethylsilylamine, trimethyl silyl ether, tetramethylsilane and the like, for instance.
It is also possible to react compounds of formulae (II) or (VIII), in the presence of compounds of formulae (V) or (IX), directly with a transition metal compound of formula (VII).
The preparation of open-chain xcfx80-complex compounds is effected by methods known to one skilled in the art, with the incorporation of donor and acceptor groups.
The present invention further relates to the use of the complex compounds described above in a method for the homo- or copolymerisation of one or more olefines, i-olefines, alkynes or diolefines as monomers, or for ring-opening addition polymerisation in a gaseous, solution, bulk, high-pressure or slurry phase at xe2x88x9260 to +250xc2x0 C. preferably up to +200xc2x0 C. and at 0.5 to 5000 bar, preferably 1 to 3000 bar, and in the presence or absence of saturated or aromatic hydrocarbons or of saturated or aromatic halogenated hydrocarbons and in the presence or absence of hydrogen. wherein said xcfx80-complex compounds are used as catalysts in an amount of 101 to 1012 moles of all the monomers per mole of xcfx80-complex, and wherein in addition the polymerisation can be conducted in the presence of Lewis acids, Brxc3x6nsted acids or Pearson acids, or can also be conducted in the presence of Lewis bases.
Examples of Lewis acids include boranes or alanes, such as aluminium alkyls, aluminium halides, aluminium alcoholates, organoboron compounds, boron halides, esters of boric acid or boron or aluminium compounds which contain both halide substituents and alkyl, aryl or alcoholate substituents, as well as mixtures thereof, or the triphenylmethyl cation. Aluminoxanes or mixtures of aluminium-containing Lewis acids with water are particularly preferred. According to current knowledge, all acids act as ionising agents which form a metallocenium cation, the charge of which is compensated for by a bulky, poorly coordinating anion.
The present invention also relates to the reaction products of ionising agents such as these with xcfx80-complexes of formula (I). These reaction products correspond to formula (XI): 
wherein
Anion represents the entire, bulky, poorly coordinating anion and Base represents a Lewis base.
The metallocene compounds of formula (I) can exist in monomeric, dimeric or oligomeric form.
Examples of poorly coordinating anions include:
B(C6H5)4, B(C6F5)4, B(CH3)(C6F5)3,

or sulphonates such as tosylates or triflates, tetrafluoroborates, hexafluorophosphates or -antimonates, perchlorates and voluminous cluster molecule anions of the carborane type, for example C2B9H12xcex8 or CB11H12xcex8. In the presence of anions such as these xcfx80-complex compounds can act as highly effective polymerisation catalysts even in the absence of aluminoxanes. This situation primarily exists if one X ligand constitutes an alkyl group or benzyl. It can, however, be advantageous to use xcfx80-complexes such as these, which comprise voluminous anions, in combination with aluminium alkyls such as (CH3)3Al, (C2H5)3Al, (n-/i-propyl)3 Al, (n-/t-butyl)3Al or (i-butyl)3Al, isomeric pentyl, hexyl or octyl aluminium alkyls, or with lithium alkyls such as methyl-Li, benzyl-Li, butyl-Li or the corresponding organo-Mg compounds, such as Grignard compounds, or organo-Zn compounds. Metal alkyls such as these firstly transfer alkyl groups to the central metal, and secondly they act as scavengers which remove water or catalyst poisons from the reaction medium or monomer during polymerisation reactions. Examples of boron compounds from which anions such as these are derived include:
triethylammonium tetraphenylborate,
tripropylammonium tetraphenyl borate,
tri(n-butyl)ammonium tetraphenylborate,
tri(t-butyl)ammonium tetraphenylborate,
N,N-dimethylanilinium tetraphenylborate,
N,N-diethylanilinium tetraphenylborate,
N,N-dimethyl(2,4,6-trimethylaluminium) tetraphenylborate,
trimethylammonium tetrakis(pentafluorophenyl)borate,
triethylammonium tetrakis(pentafluorophenyl)borate,
tripropylammonium tetrakis(pentafluorophenyl)borate,
tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate.
tri(sec-butyl)ammonium tetrakis(pentafluorophenyl)borate,
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,
N,N-diethylaluminium-tetrakis(pentafluorophenyl)borate,
N,N-dimethyl(2,4,5-trimethylaluminium)tetrakis(pentafluorophenyl)borate,
trimethylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
triethylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
tripropylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
tri(n-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
dimethyl(t-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
N,N-dimethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
N,N-diethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate,
N,N-dimelthye-(2,4,6-trimethyl(anilinium)-tetrakis-(2,3,4,6-tetraflurophenylborate)dialkylammonium salts, such as:
di-(i-propyl)ammonium tetrakis(pentafluorophenyl)borate and
dicyclohexylammonium -tetrakis(pentafluorophenyl)borate,
tri-substituted phosphonium salts, such as:
triphenylphosphonium tetrakis(pentafluorophenyl)borate,
tri(o-tolyl)phosphonium tetrakis(pentafluorophenyl)borate,
tri(2,6-dimethylphenyl)phosphonium tetrakis(pentafluorophenyl)borate,
tritolylmethyl tetrakis(pentafluorophenyl)borate,
triphenylmethyl tetraphenylborate (trityl tetraphenylborate),
trityl tetrakis(pentafluorophenyl)borate,
silver tetrafluoroborate,
tris(pentafluorophenyl)borane,
tris(trifluoromethyl)borane.
The xcfx80-complex compounds or metallocene compounds according to the invention can be used for (co)polymerisation after they have been isolated as the pure substances. It is also possible, however, to produce and use them xe2x80x9cin situxe2x80x9d in the (co)polymerisation reactor in the manner known to one skilled in the art.
The xcfx80-complex compounds according to the invention are characterised by the presence of at least one coordinate bond between the donor atom(s) D and the acceptor atom(s) A. Both D and A can be substituents of the xcfx80I or xcfx80II xcfx80 systems which are associated with them, or can be part of the xcfx80 system, wherein at least one of D and A is part of the xcfx80 system, however. The xcfx80 system here is to be understood as the entire system which is optionally singly- or doubly-condensed. The following embodiments result therefrom:
D is part of the xcfx80 system, A is a substituent of the xcfx80 system;
D is a substituent of the xcfx80 system, A is part of the xcfx80 system;
D and A are parts of their respective xcfx80 system.
The following are examples of heterocyclic ring systems in which D or A are part of the ring system: 
The important heterocyclic ring systems are the systems denoted by (a), (b), (c), (d), (g), (m), (n) and (o); those systems denoted by (a), (b), (c) and (m) are particularly important.
If one of D and A is a substituent of its associated ring system, the ring, system is a 3-, 4-, 5-, 6-, 7- or 8-membered ring system, with or without an electrical charge, which can be further substituted and/or condensed in the manner described, 5- and 6-membered ring systems are preferred. The negatively charged cyclopentadienyl system is particularly preferred.
The first or second xcfx80 system, namely xcfx80I and xcfx80II respectively, if it is formed as a ring system and if one of D and A is a substituent of the ring system may for example be one of the group comprising cyclopentadiene, substituted cyclopentadiene, indene. substituted indene, fluorene and substituted fluorene. Substituents can replace one to all of the H atoms of the ring system. These substituents may be a C1-C20 alkyl such as methyl, ethyl, propyl, isopropyl, butyl or iso-butyl, t-butyl, hexyl, octyl, decyl, trimethylsilyl, pentamethyldisilanyl, trimethylsilyl-methyl, dodecyl, hexadecyl, octadecyl or eicosyl, a C6-C12 aryl such as phenyl, a C1-C4 alkylphenyl, such as tolyl, ethylphenyl, (i-)propylphenyl, (i-,tert.-)butyl phenyl or xylyl, a halogenoaryl, such as fluoro-, chloro- or bromophenyl, naphthyl or biphenylyl, or a triorganyl-silyl such as trimethylsilyl (TMS), or ferrocenyl, as well as D or A as defined above. Condensed-on rings can be either unsaturated, e.g. aromatic rings, or can be partially or completely hydrogenated, so that only the double bond remains which is shared by both the condensed-on ring and the cyclopentadiene ring. Furthermore, benzene rings as in indene or fluorene may contain one or two further condensed-on benzene rings. In addition to this, the cyclopentadienyl ring and a condensed-on benzene ring may jointly contain a further benzene ring which is condensed on.
In the form of their anions, cyclopentadiene skeletons are excellent ligands for transition metals, wherein each cyclopentadienyl carbanion of the aforementioned, optionally substituted form compensates for a positive charge of the central metal in the complex Individual examples of carbanions such as these include: cyclopentadienyl, methyl-cyclopentadienyl 1,2-dimethyl-cyclopentadienyl, 1,3-dimethyl-cyclopentadienyl, indenyl, phenylindenyl, 1,2-diethyl-cyclopentadienyl, tetramethyl-cyclopentadienyl, ethyl-cyclopentadienyl, n-butyl-cyclopentadienyl, n-octyl-cyclopentadienyl, xcex2-phenylpropyl-cyclopentadienyl, tetrahydroindenyl, propyl-cyclopentadienyl, t-butyl-cyclopentadienyl, benzyl-cyclopentadienyl, diphenylmethyl-cyclopentadienyl, trimethylgermyl-cyclopentadienyl, trimethylstannyl-cyclopentadienyl, trifluoromethyl-cyclopentadienyl, trimethylsilyl-cyclopentadienyl, pentamethylcyclopentadienyl, fluorenyl, tetrahydro- or octahydrofluorenyl, fluorenyls and indenyls which are benzo-annulated on the six-membered ring, N,N-dimethylamino-cyclopentadienyl, dimethylphosphino-cyclopentadienyl, methoxy-cyclopentadienyl dimethylboranyl-cyclopentadienyl and (N,N-dimethylantinomethyl)-cyclopentadienyl.
In addition to the first donor-acceptor bond between D and A which is obligatorily present, further donor-acceptor bonds can be formed if additional D and/or A entities are present as substituents or as parts of the respective xcfx80 system. All the donor-acceptor bonds are characterised by their reversibility, as explained above. D or A independently of each other, can be situated on the metal-bonded xcfx80 system or on a condensed-on ring or in a condensed-on ring or in another substituent of xcfx80I or xcfx80II. If a plurality of D or A entities is present, these can assume positions different to those cited above. The present invention accordingly comprises both the bridged molecular states (Ia) and the unbridged states (Ib). The number of D groups can be the same as or different from the number of A groups. Preferably, only one D/A bridge is present.
In addition to the D/A bridges according to the invention, covalent bridges can also be present. In this situation the D/A bridges increase the stereorigidity and the thermal stability of the catalyst. By alternating between a closed and an open D/A bond. sequential polymers of higher and lower stereoregularity can be obtained. Sequences such as these can have different chemical compositions in copolymers.
Suitable donor groups are mainly those in which the donor atom D is an element of main groups 5, 6 or 7 of the periodic table (Mendeleev) and comprises at least one free electron pair, wherein for elements of main group 5 the donor atom is in a state of bonding with substituents, and for elements of main group 6 the donor atom is in a state of bonding such as this. Donor atoms of main group 7 do not bear substituents. This is clarified below, using phosphorus P, oxygen O and chlorine Cl as examples of donor atoms, wherein xe2x80x9cSubst.xe2x80x9d denotes said substituents and xe2x80x9cxe2x88x92xcfx80Ixe2x80x9d denotes the bond to the xcfx80 system, a line with an arrow has the meaning of a coordinate bonds as given in formula (I) and other lines denote electron pairs which are present: 
The groups which are mainly suitable as acceptor groups are those in which the acceptor atom A is an element of main group 3 of the periodic table of the elements (Mendeleev), such as boron aluminium, gallium, indium or thallium, is in a state of bonding with substituents, and comprises an electron vacancy.
D and A are linked by a coordinate bond, which is also termed a dative bond, wherein D assumes a positive (partial) charge and A assumes a negative (partial) charge.
Accordingly, a distinction is made between the donor atom D and the donor group or between the acceptor atom A and the acceptor group. The coordinate bond Dxe2x86x92A is formed between the donor atom D and the acceptor atom A. The expression xe2x80x9cdonor groupxe2x80x9d means the unit comprising the donor atom D, the substituents which are optionally present and the electron pairs which are present: correspondingly, xe2x80x9cacceptor groupxe2x80x9d means the unit comprising the acceptor atom A the substituents which are optionally present and the electron vacancy which is present.
The bond between the donor atom or the acceptor atom of the D or A substituent and the ring system can be interrupted by spacer groups in the sense of D-spacer-xcfx80I or A-spacer-xcfx80II. In the third of the above examples of formulae, xe2x95x90C(R)xe2x80x94 represents a spacer such as this between O and xcfx80I. Examples of other spacer groups include:
dimethylsilyl,
diethylsilyl,
di-n-propylsilyl,
diisopropylsilyl,
di-n-butylsilyl,
di-t-butylsilyl,
di-n-hexylsilyl,
methylphenylsilyl,
ethylmethylsilyl,
diphenylsilyl
di(p-t-butylphenethylsilyl),
n-hexylmethylsilyl
cyclopentamethylenesilyl,
cyclotetramethylenesilyl,
cyclotrimethylenesilyl,
dimethylgermanyl,
diethylgermanyl,
phenylamino,
t-butyl amino,
methylamino,
t-butylphosphino,
ethylphosphino,
phenylphosphino,
methylene,
dimethylmethylene (i-propylidene),
diethylmethylene,
ethylene,
dimethylethylene,
diethylethylene,
dipropylethylene,
propylene,
dimethylpropylene,
diethylpropylene,
1,1-dimethyl-3-3-dimethylpropylene,
tetramethyldisiloxane
1,1,4,4-tetramethyldisilylethylene,
diphenylmethylene.
D or A are preferably bonded to the respective xcfx80 system without spacer groups.
D and A, independently of each other, can be situated on the cyclopentadienyl ring or on a condensed-on benzene ring or on another substituent of xcfx80I and xcfx80II, respectively. If a plurality of D or A entities is present, they can assume various of the cited positions.
Examples of substituents on the donor atoms N, P, As, Sb, Bi, O, S, Se or Te and on the acceptor atoms B, Al, Ga, In or TI include: C1-C12(cyclo)alkyl, such as methyl, ethyl, propyl, i-propyl, cyclopropyl, butyl, i-butyl , tert.-butyl , cyclobutyl, pentyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, isomeric heptyl, octyl, nonyl, decyl and undecyl groups, and dodecyl; the C1-C12 alkoxy groups which correspond thereto; vinyl, butenyl, allyl; C6-C12 aryl, such as phenyl, naphthyl or biphenylyl, or benzyl, which can be substituted by halogens, by 1 or 2 C1-C4 alkyl groups, by C1-C4 alkoxy groups, by sulphonate, nitro or halogenoalkyl groups, or by C1-C6 alkyl-carboxy, C1-C6 alkyl-carbonyl or cyano (e.g. perfluorophenyl, m,mxe2x80x2-bis(trifluoromethyl)-phenyl, tri(C1-C20 alkyl)silyl, tri(C6-C12 aryl)silyl and analogous substituents familiar to one skilled in the art); analogous aryloxy groups: indenyl; halogens such as F, Cl, Br and I, 1-thienyl, disubstituted amino, such as (C1-C12 alkyl)2amino, diphenylamino, tris-(C1-C12 alkyl)-silyl, NaSO3-aryl, such as NaSO3-phenyl and NaSO3-tolyl, C6H5xe2x80x94Cxe2x89xa1Cxe2x80x94; aliphatic and aromatic C1-C20 silyl, the alkyl substituents of which, in addition to those cited above, may comprise octyl, decyl, dodecyl, stearyl or eicosyl, and the aryl substituents of which may comprise phenyl, tolyl, xylyl, naphthyl or biphenylyl; and substituted silyl groups which are bonded to the donor or acceptor atom via xe2x80x94CH2xe2x80x94, for example (CH3)3SiCH2xe2x80x94, (C1-C12 alkyl)(phenyl)amino, (C1-C12 alkyl)(naphthyl)amino, (C1-C12 alkylphenyl)2amino, C6-C12 aryloxy comprising the aforementioned aryl groups, C1-C8 perfluoroalkyl and perfluorophenyl. The preferred substituents are: C1-C6 alkyl, C5-C6 cycloalkyl, phenyl, tolyl, C1-C6 alkoxy, C6-C12 aryloxy, vinyl, allyl, benzyl, perfluorophenyl, F, Cl, Br, di-(C1-C6 alkyl)-amino and diphenylamino.
Donor groups are those in which the free electron pair is located on the N, P, As, Sb, Bi, O, S, Se, Te, F, Cl, Br or I; of the latter, N, P, O and S are preferred. Examples of donor groups include: (CH3)2Nxe2x80x94, (C2H5)2Nxe2x80x94, (C3H7)2Nxe2x80x94, (C4H9)2Nxe2x80x94, (C6H5)2Nxe2x80x94, (CH3)2Pxe2x80x94, (C2H5)2Pxe2x80x94, (C3H7)2Pxe2x80x94, (i-C3H7)2Pxe2x80x94, (C4H9)2Pxe2x80x94, (t-C4H9)2Pxe2x80x94cyclohexyl2Pxe2x80x94, (C6H5)2Pxe2x80x94, (CH3)(C6H5)Pxe2x80x94, (CH3O)2Pxe2x80x94, (C2H5O)2Pxe2x80x94, (C6H5O)2Pxe2x80x94, (CH3-C6H4xe2x80x94O)2Pxe2x80x94, ((CH3)2N)2Pxe2x80x94, phosphino groups which contain methyl, CH3Oxe2x80x94, CH3Sxe2x80x94, C6H5Sxe2x80x94, xe2x80x94C(C6H5)xe2x95x90O, xe2x80x94C(CH3)xe2x95x90O, xe2x80x94OSi(CH3)3 and xe2x80x94OSi(CH3)2-t-butyl, in which N and P each comprise one free electron pair and O and S each comprise two free electron pairs, and wherein in the two last-mentioned examples the doubly bonded oxygen is bonded via a spacer group, as well as systems such as the pyrrolidone ring, wherein the different ring members likewise act as spacers.
Acceptor groups are those in which an electron pair vacancy is present on the B, Al, Ga, In or Tl, preferably B, Al, Ga. In most preferably B, Al or Ga examples include: (CH3)2Bxe2x80x94, (C2H5)2Bxe2x80x94, H2Bxe2x80x94, (C6H5)2Bxe2x80x94, (CH3)(C6H5)Bxe2x80x94, (vinyl)2Bxe2x80x94, (benzyl)2Bxe2x80x94, Cl2Bxe2x80x94(CH3O)2Bxe2x80x94, Ci2Alxe2x80x94, (CH3)2Alxe2x80x94, (i-C4H9)2Alxe2x80x94, (Cl)(C2H5)Alxe2x80x94, (CH3)2Gaxe2x80x94, (C3H7)2Gaxe2x80x94, ((CH3)3Sixe2x80x94CH2)2Gaxe2x80x94, (vinyl)2Gaxe2x80x94, (C6H5)2Gaxe2x80x94, (CH3)2Inxe2x80x94, ((CH3)3xe2x80x94SiCH2)2Inxe2x80x94 and (cyclopentadienyl)2Inxe2x80x94.
Suitable donor and acceptor groups also comprise those which contain chiral centres. Other suitable donor and acceptor groups are those in which both substituents jointly form a ring with the D or A atom. Examples thereof include 
According to the invention, one or both xcfx80 systems xcfx80I or xcfx80II can exist as heterocycles in the form of the aforementioned ring systems (a) to (r). In this situation, D is preferably an element of main groups 5 or 6 of the periodic table of the elements (Mendeleev); A is preferably boron here. Specific examples of hetero xcfx80 systems such as these, particularly heterocycles, include: 
wherein
R, Rxe2x80x2=H, alkyl, aryl or alkaryl, e.g., methyl, ethyl, t-butyl, phenyl, o,oxe2x80x2-di-(i-propyl)-phenyl.
Examples of heterocycles include: pyrrolyl, methylpyrrolyl, dimethylpyrrolyl, trimethylpyrrolyl, tetramethylpyrrolyl, t-butylpyrrolyl, di-t-butylpyrrolyl, indolyl, methylindolyl, dimethylindolyl, t-butylindolyl, di-t-butylindolyl, tetramethylphospholyl, tetraphenylphospholyl, triphenylphospholyl, trimethylphospholyl, phosphaindenyl, dibenzophospholyl(phosphafluorenyl) and dibenzopyrrolyl.
Examples of preferred donor-acceptor bridges between xcfx80I and xcfx80II include the following:
Nxe2x86x92B, Nxe2x86x92Al, Pxe2x86x92B, Pxe2x86x92Al, Oxe2x86x92B, Oxe2x86x92Al, Clxe2x86x92B, Clxe2x86x92Al, Cxe2x95x90Oxe2x86x92B, Cxe2x95x90Oxe2x86x92Al,
wherein both atoms of these donor-acceptor bridges can be part of a hetero xcfx80 system, or wherein one (donor or acceptor) atom is part of a xcfx80 system and the other is a substituent of the second xcfx80 system, or wherein both atoms are substituents of their respective ring and one of the rings additionally contains a hetero atom.
In accordance with the explanation given above, the two ligand systems xcfx80I and xcfx80II can be linked by one, two or three donor-acceptor bridges. This is possible because according to the invention formula (Ia) contains the Dxe2x86x92A bridge explained above. but the ligand systems xcfx80I and xcfx80II can also comprise further D and A entities as substituents or hetero xcfx80-centres. The number of additional Dxe2x86x92A bridges which result therefrom is zero, one or two. The number of D or A substituents on xcfx80I and xcfx80II, respectively, can be the same or different. The two ligand systems xcfx80I and xcfx80II may be covalently bridged in addition (the spacer groups described in detail above are examples of covalent bridges). Compounds without a covalent bridge are preferred. however, in which xcfx80I and xcfx80II are accordingly linked via a donor-acceptor bridge only.
M represents a transition metal of subgroups 3, 4, 5 or 6 of the periodic table of the elements (Mendeleev), including the lanthanides and actinides: examples thereof include Sc, Y, La, Sm, Nd, Lu, Ti, Zr, Hf, Th, V, Nb, Ta and Cr, Ti, Zr, Hi, V, Nb and Ta are preferred.
On the formation of the xcfx80-complex compounds according to the invention, particularly those with a metallocene structure, each positive charge of the transition metal M is compensated for by a xcfx80 system in each case, particularly by a carbanion which contains a cyclopentadienyl group.
Any remaining positive charges on the central atom M are neutralised by other anions X, which are generally monovalent, two identical or different anions of which can also be linked to each other 
Examples thereof include monovalent or negative radicals from identical different, linear or branched, saturated or unsaturated hydrocarbons, amines, phosphines, thio alcohols, alcohols or phenols, Simple anions such as CR3xe2x88x92, NR2xe2x88x92, PR2xe2x88x92, ORxe2x88x92, SRxe2x88x92, etc., can be bonded by saturated or unsaturated hydrocarbon or silane bridges, whereupon dianions are formed and the number of bridging atoms can be 0, 1, 2, 3, 4, 5 or 6, 0 to 4 bridging atoms are preferred, and 1 or 2 bridging atoms are particularly preferred. Apart from H atoms, the bridging atoms may also bear further hydrocarbon substituents R. Examples of bridges between simple anions include xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94(CH2)3xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94(CHxe2x95x90CH)2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94CH2xe2x80x94, xe2x80x94CH2xe2x80x94CHxe2x95x90CHxe2x80x94CH2xe2x80x94, xe2x80x94Si(CH3)2xe2x80x94 and xe2x80x94C(CH3)2xe2x80x94. Examples of X include hydride, chloride, methyl, ethyl phenyl, allyl benzyl, cyclopentadienyl, fluoride, bromide, iodide, the n-propyl radical, the i-propyl radical, the n-butyl radical, the amyl radical, the i-amyl radical, the hexyl radical, the i-butyl radical, the heptyl radical, the octyl radical, the nonyl radical, the decyl radical, the cetyl radical, methoxy, ethoxy, propoxy, butoxy, phenoxy, the analogous, S-based thioalcoholates, dimethylamino, diethylamino, methylethylamino, di-t-butylamino, diphenylamino, diphenylphosphino, dicyclohexylphosphino, dimethylphosphino, methylene, ethylidene, propylidene, butadienediyl, and the ethylene glycol dianion. Examples of dianions include 1,4-diphenyl-1,3-butadiendiyl, 3-methyl-1,3-pentadiendiyl, 1,4-dibenzyl-1,3-butadienediyl, 2,4-hexadiendiyl, 1,3-pentadiendiyl, 1,4-ditolyl-1,3-butandienediyl, 1,4-bis(trimethylsilyl)-1,3-butadienediyl, and 1,3-butadiendiyl. Other examples of dianions are those which comprise hetero atoms, for instance those of structure 
wherein the bridge has the meaning given above, 1,4-diphenyl-1,3-butadienediyl, 1,3-pentadienediyl, 1,4-dibenzyl-1,3-butadienediyl, 2,4-hexadienediyl, 3-methyl-1,3-pentadienediyl, 1,4-ditolyl-1,3-butadienediyl and 1,4-bis(trimethylsilyl)-1,3-butadienediyl are particularly preferred. Furthermore, weakly coordinating or non-coordinating anions of the aforementioned type are particularly preferred for charge compensation.
Activation through voluminous anions such as these is achieved by the reaction of D/A xcfx80 -complex compounds, particularly D/A-metallocenes, with tris-(pentafluorophenyl)-borane, triphenylborane, triphenylaluminium, trityl-tetrakis-(pentafluorophenyl)-borate or N,N-dialkyl-phenyl-ammonium tetrakis-(pentafluorophenyl)borate or with the corresponding phosphonium or sulphonium salts of borates or with alkali, alkaline earth, thallium or silver salts of borates, carboranes, tosylates, triflates, perfluorocarboxylates such as trifluoroacetate, or with the corresponding acids, D/A-metallocenes in which at least one anion equivalent X constitutes alkyl, aryl or benzyl groups are preferably used here. Derivatives such as these can also be produced xe2x80x9cin situxe2x80x9d by the prior reaction of D/A xcfx80-complex compounds, particularly D/A metallocenes comprising other anion equivalents such as X=F, Cl, Br, OR NR2, etc, with aluminium alkyls, organolithium compounds, Mg Grignard compounds or zinc or lead alkyls. The reaction products which can be obtained therefrom can be activated, without prior isolation, with the aforementioned boranes or borates.
Depending on the charge on M, the suffix n assumes the value zero, one, two, three or four, preferably zero, one or two. In particular, and depending on which subgroup they belong to, the aforementioned subgroup metals can assume valencies or charges from two to six, preferably two to four, two of which are usually compensated by the carbanions of the metallocene compound. In the case of Ti3xe2x88x92 or La3xe2x88x92, the suffix n assumes a value of one, and in the case of Zr4+ it assumes a value of two: for Ti2+ or Sm2xe2x88x92 n becomes zero
In the method of preparing xcfx80-complex compounds, particularly metallocene compounds of formula (I), a reaction can be effected either between a compound each of formulae (II) and (III) given above, or between a compound each of formulae (IV) and (V) given above, or between a compound each of formulae (VI) and (VII) given above, or between a compound each of formulae (VIII) and (III) given above or between a compound each of formulae (IV) and (IX) given above, or between a compound each of formulae (X) and (VII) given above, with the separation or splitting-off of alkali metal-X, alkaline earth metal-X2, silyl-X, germyl-X, stannyl-X or HX compounds in an aprotic solvent at temperatures from xe2x88x9278xc2x0 C. to +120xc2x0 C., preferably from xe2x88x9240xc2x0 C. to +70xc2x0 C., and at a molar ratio of (II):(III) or (IV):(V) or (VI):(VII) or (VIII):(III) or (IV):(IX) or (X):(VII) of 1:0.5-2, preferably 1:0.8-1.2, most preferably 1:1. In situations comprising the reaction of (VIII) with (III) or (IV) with (IX) or (X) with (VII), it is possible to dispense with an aprotic solvent if (VIII), (IX) or (X) is liquid under the reaction conditions. Examples of separated or split-off compounds such as these include: TlCl, LiCl, LiBr, LiF, LiI, NaCl, NaBr, KCl, KF, MgCl2, MgBr2), CaCl2, CaF2, trimethylchlorosilane, triethylchlorosilane, tri-(n-butyl)chlorosilane, triphenylchlorosilane, trimethylchlorogermane, trimethylchlorostannane, di-methylamine, diethylamine, dibutylamine and other compounds which can be identified by one skilled in the art from the aforementioned pattern of substitution.
Compounds of formulae (II) or (IV) are thus preferably composed of aromatic anions with a cyclopentadienyl skeleton or a heterocyclic skeleton, which contain 1 to 3 donor groups as substituents which are employed for the formation of D/A bridges and which are covalently bonded or are incorporated as members of heterocyclic rings, wherein according to the invention at least one aromatic anion constitutes a heterocyclic skeleton such as this, and said compounds comprise a cation as a counterion for the negative charge of the cyclopentadienyl skeleton. Compounds of formula (VIII) are uncharged cyclic skeletons which also comprise 1 to 3 donor groups which are used for the D/A bridge bond, but which have detachable groups E(R1R2R3) which are easily separable, such as silyl, germyl or stannyl groups or hydrogen, instead of ionic groups.
The second component for the formation of metallocene compounds, namely the compound of formulae (III) or (V), is likewise composed of an aromatic anion, which is identical to the cyclic skeleton of compound (II) or (IV) or is different therefrom, but which instead of donor groups bears 1 to 3 acceptor groups for the D/A bridge bond. which are incorporated either as substituents or as hetero atoms. In a corresponding manner, compounds of formula (IX) are uncharged skeletons which comprise 1 to 3 acceptor groups which are used for the D/A bridge bond and which also comprise detachable groups F(R4R5R6) which are easily separable.
In a completely analogous manner, compounds of formulae (VI) or (X) constitute starting materials with a pre-formed Dxe2x86x92A bond, are anion-countercation compounds or uncharged skeletons with a total of 1 to 3 possible Dxe2x86x92A bonds, and form metallocene compounds (I) by reaction with compounds of formula (VII).
The two starting materials for the method of production, namely (II) and (III) or (IV) and (V) or (VI) and (VII) or (VIII) and (III) or (IV) and (IX) or (X) and (VII), react spontaneously when placed in contact, with the simultaneous formation of the donor-acceptor-group -Dxe2x86x92A- or with complexing of the metal cation M with the separation of M1X or E(R1R2R3)X or F(R4R5R6)X or HX. In the illustration of the donor-acceptor-group, the substituents on D and A have been omitted for the sake of clarity.
Mxe2x80x2 is a cation equivalent of an alkali or alkaline earth metal, such as Li, Na, K, xc2xdMg, xc2xdCa, xc2xdSr, xc2xdBa, or thallium.
The solvents for the method of production are aprotic, polar or nonpolar solvents such as aliphatic and aromatic hydrocarbons or aliphatic and aromatic halogenated hydrocarbons, and ethers including cyclic ethers. In principle, other aprotic solvents, such as those known to one skilled in the art, are also suitable, but those with boiling points which are too high are less preferred in the interest of simplicity of work-up. Examples of suitable solvents include n-hexane, cyclohexane, pentane, heptane, petroleum ether, toluene, benzene, chlorobenzene, methylene chloride, diethyl ether, tetrahydrofuran and ethylene glycol dimethyl ether.
The starting materials of formulae (II), (III), (IV) and (V) for the method of production can be prepared by methods known from the literature or analogously thereto. Thus, for example, by employing a procedure analogous to that described in J. of Organometallic Chem. (1971), 29, 227, commercially available trimethylsilyl-cyclopentadiene can be reacted firstly with butyllithium and then with trimethylsilyl chloride to form bis(trimethylsilyl)-cyclopentadiene The latter can in turn be reacted with boron trichloride to form trimethylsilyl-cyclopentadienyl-dichloroborane (analogously to J. of Organometallic Chem. (1979), 169, 327), which can finally be reacted with titanium tetrachloride, analogously to the procedure described in J. of Organometallic Chem. (1979), 169, 373 to form dichloroboryl-cyclopentadienyl-titanium trichloride. The last-mentioned compound already constitutes a prototype of compounds of formula (III), and furthermore can undergo a selective reaction with trimethylaluminium, whereupon the two chlorine atoms bonded to the boron atom are replaced by methyl groups and whereupon a further compound of formula (III) is formed. Under process conditions analogous to those described in J. Amer. Chem. Soc. (1983) 105 3882 and Organometallics (1982) I, 1591, commercially available cyclopentadienyl-thallium can be reacted with chlorodiphenylphosphine and can be further reacted with butyllithium, whereupon a prototype of compounds of formula (II) is obtained.
As a further example mention should be made of the formation of dimethylstannyl-diphenylphosphine-indene, by the reaction of indene firstly with butyllithium as cited above and subsequently with chlorodiphenylphosphine. Further reaction , firstly with butyllithium again and then with chlorotributyltin, results in the aforementioned compound, which after further reaction with zirconium tetrachloride yields diphenylphosphino-indenyl-zirconium trichloride as a representative of compounds of formula (IV). Syntheses and methods of preparation such as these are familiar to one skilled in the art in the field of organometallic and organo-elemental chemistry, and have been published in numerous literature references, only some of which are listed above by way of example.
The Examples which are described in detail below show how heterocyclic precursors or catalysts according to the invention can be obtained. Thus pyrrolyl-lithium (formula II) can be produced from pyrrole by reaction with butyllithium, as described in J. Amer. Chem. Soc. (1982), 104, 2031, for instance. Trimethylstannyl-phosphol (formula VIII) is obtained by the reaction of 1-phenylphosphol with lithium followed by aluminium trichloride, whereupon phospholyl-lithium (formula II) is produced, which in turn reacts further with trimethylchlorostannane to form trimethylstannyl-phosphol; see J. Chem. Soc. Chem. Comm. (1988), 770. This compound can be reacted with titanium tetrachloride to form phospholyl-titanium trichloride (formula IV).
The xcfx80-complex compounds according to the invention, particularly the metallocene compounds, are outstandingly suitable as catalysts in processes for the homo- and copolymerisation of one or more C2-C40 olefines, or for the copolymerisation of one or more C2-C40 olefines with one or more C4-C8 isoolefines, C2-C8 alkynes or C4-C8 diolefines, in a gaseous, solution, bulk, high-pressure or slurry phase at xe2x88x9260 to +250xc2x0 C. and at a pressure of 0.5 to 5000 bar, wherein the polymerisation can be conducted in the presence or absence of linear or branched, saturated, aromatic or alkyl-substituted aromatic C1-C20 hydrocarbons or of saturated or aromatic C2-C10 halogenated hydrocarbons. Polymerisation processes such as these can be conducted batch-wise but are preferably conducted continuously, 101 to 1012 moles of (co)monomers are reacted per mole of metallocene compounds. The xcfx80-complex compounds according to the invention, particularly the metallocene compounds, can be used together with co-catalysts. The quantitative ratio of xcfx80-complex compound to co-catalyst ranges from 1 to 100,000 moles of co-catalyst per mole of xcfx80-complex. Aluminoxane compounds are examples of co-catalysts. These should be understood to include those of formula 
wherein
R represents a C1-C20 alkyl a C6-C12 aryl or benzyl, and
n denotes a number from 2 to 50, preferably 10 to 35.
It is also possible to use a mixture of different aluminoxanes or a mixture of precursors thereof (aluminium alkyls or alkylaluminium halides) in combination with water (in gaseous, liquid or solid form, or in bound form, as water of crystallisation for instance) Water can also be introduced as residual moisture of the polymerisation medium, of the monomer or of a support such as silica gel.
The bonds which protrude from the square brackets of formula (XII) contain R groups or AlR2 groups as terminal groups of the oligomeric aluminoxane. Aluminoxanes such as these generally exist as a mixture of a plurality thereof which have different chain lengths. Detailed research has also resulted in aluminoxanes with a ring-like or cage-like structure. The latter are preferred Aluminoxanes are commercially available compounds. In the particular case when Rxe2x95x90CH3, they are referred to as methylaluminoxanes (MAOs).
Other co-catalysts include aluminium alkyls, lithium alkyls or organo-Mg compounds such as Grignard compounds, or partially hydrolysed organoboron compounds. The preferred co-catalysts are aluminoxanes.
Activation with the co-catalyst, or the production of the voluminous, non-coordinating or weakly coordinating anion, can be effected in an autoclave or in a separate reaction vessei (pre-formation). Activation can be effected in the presence or absence of the monomer or monomers to be polymerised. Activation can be effected in an aliphatic, aromatic or halogenated solution or suspension medium or on the surface of a catalyst support material.
The xcfx80-complex compounds and the co-catalysts can either be used as such in homogeneous or heterogeneous form, or can also be used, individually or jointly, in heterogeneous form on supports. The support material here can be of an inorganic or organic nature, such as silica gel, Al2O3, MgCl2, cellulose derivatives, starch and polymers. Either the xcfx80-complex compound can first be deposited on the support, or the co-catalyst, e.g. the aluminoxane and/or aluminium alkyl, can first be deposited on the support, and the other component(s) in each case can be added thereafter. In a similar manner, however, the xcfx80-complex compound in homogeneous or heterogeneous form can be activated with the co-catalyst and the activated xcfx80-complex compound can be deposited on the support thereafter.
The support materials are preferably subjected to thermal and/or chemical pretreatment in order to set the water content or the OH group concentration to a defined value or to keep these values as low as possible. Chemical pretreatment may comprise the reaction of the support with an aluminium alkyl, for example. Inorganic supports are usually heated to 100xc2x0 C. to 1000xc2x0 C. for 1 to 100 hours before use. The specific surface of inorganic supports such as these, particularly of silica (SiO2), is between 10 and 1000 m2/g, and is preferably between 100 and 800 m2/g. The particle diameter is between 0.1 and 500 micrometres (xcexc), preferably between 10 and 200xcexc.
Examples of olefines, i-olefines, alkynes and diolefines which can be reacted by homo- or copolymerisation include ethylene, propylene, butene-1, i-butene, pentene-1, hexene-1, octene-1, 3-methyl-butene-1, 4-methyl-pentene-1, 4-methyl-hexene-1, 1,3-butadiene, isoprene, 4-methyl-1,3-pentadiene, 1,4-hexadiene, 1,5-hexadiene and 1,6-octadiene, chloroprene, acetylene and methylacetylene. With xcex1,xcfx89-diolefines, cyclisation polymerisation can be effected in addition, wherein poly-(methylene-1,3-cyclopentane) can be formed from 1,5-hexadiene for example: 
If trialkylsilyl-substituted, xcex1xcfx89-diolefines are used in this context, a functional group can subsequently be introduced by a reaction analogous to polymerisation. Moreover, olefines and diolefines such as these can be substituted, for example with phenyl, substituted phenyl, halogens, an esterified carboxyl group or an acid anhydride group. Examples of compounds of this type include styrene, o-, m- and p-methylstyrene, 2,4-, 2,5-, 3,4- and 3,5-dimethylstyrene, m- and p-ethylstyrene, p-tert-butyl styrene, m- and p-divinylbenzene, trivinylbenzene, o-, m- and p-chlorostyrene, o-, m- and p-bromostyrene, o-, m- and p-fluorostyrene, o-methyl-p-fluorostyrene, o-, m- and p-methoxystyrene, o-, m- and p-ethoxystyrene, indene, 4-vinyl-biphenyl, vinyl-fluorene, vinyl-anthracene, methyl methacrylate, ethyl acrylate, vinylsilane, trimethylallylsilane, vinyl chloride, vinylidene chloride, tetrafluoroethylene, isobutylene, vinyl carbazole, vinyl pyrrolidone, acrylonitrile, vinyl ethers and vinyl esters. Furthermore, ring-opening addition polymerisation is possible according to the invention, for instance of lactones such as xcex5-caprolactone or xcex4-valerolactone, or of lactams such as xcex5-caprolactam. The preferred monomers are: ethylene, propylene, butene, hexene, octene, 1,3-butadiene, isoprene, 1,5-hexadiene, 1,6-octadiene, styrene and the aforementioned p-substituted styrenes, methyl methacrylate, xcex5-caprolactone, xcex4-valerolactone and acetylene. The preferred copolymers are produced from the following monomer systems: ethylene/styrene, ethylene/butadiene, butadiene/styrene, isoprene/styrene, 4-methyl-1,3-penta-diene/styrene, styrene/substituted styrene, maleinimide/styrene and acrylonitrile/styrene. The possibility of producing highly syndiotactic polystyrenes is of great importance These have a degree of syndiotacticity such that the content of racemic diadene is at least 75%, preferably at least 85%, and the content of racemic pentadene is at least 30%, preferably at least 50%. The possibility of producing pure poly-(1,3-dienes) is also important, particularly those which comprise a high degree of 1,3-cis-linking. Other important poly-(1,3-dienes) are those which comprise 1,2-linking, and which accordingly give rise to unsaturated side chains.
It is possible to conduct the aforementioned (co)polymerisation processes in the presence of hydrogen, in order to adjust the molecular weights or to increase the activity, for instance.
The homo- or copolymerisation or addition polymerisation processes which can be effected with the xcfx80-complex compounds according to the invention, particularly with metallocene compounds, are conducted within the range from xe2x88x9260 to +250xc2x0 C., preferably 50 to 200xc2x0 C. and at 0.5 to 5000 bar, preferably 1 to 3000 bar, either adiabatically or isothermally. These processes include high-pressure processes in autoclaves or tubular reactors, processes in solution and bulk polymerisation processes, processes conducted in a slurry phase in stirred reactors or loop-type reactors, and processes in the gas phase, wherein the pressures employed in the slurry, solution or gas phase do not exceed 65 bar. Polymerisation processes such as these can also be conducted in the presence of hydrogen. All these processes have long been known and are familiar to one skilled in the art. One advantage of the xcfx80-complex compounds according to the invention is that by selecting their substituents they can be produced either as soluble xcfx80-complex compounds which are optionally deposited on supports, or can also be produced as insoluble xcfx80-complex compounds Soluble xcfx80-complex compounds can be used for high-pressure processes and solution processes. Heterogeneous xcfx80-complex compounds can be used in the gas phase, for example.
Due to their donor-acceptor bridge, the xcfx80-complex compounds according to the invention enable a defined opening of the two cyclopentadienyl skeletons to occur in the manner of a law, wherein, apart from a high activity, a high degree of stereoselectivity, a controlled molecular weight distribution and the uniform incorporation of comonomers are ensured. As a result of this defined, jaw-like opening process, there is also space for voluminous comonomers. Moreover, a high degree of uniformity of molecular weight distribution results from the uniform, defined site of polymerisation which occurs by insertion (single site catalyst).
The D/A structure can result in the additional stabilisation of these catalysts up to high temperatures, so that these catalysts can also be used in the high temperature range from 80 to 250xc2x0 C., preferably 80 to 180xc2x0 C. The possible thermal dissociation of the donor-acceptor bond is reversible, and on account of this self-organisation process and self-repair mechanism results in catalyst properties of particularly high quality. Thermal dissociation makes it possible, for example, to achieve a targeted broadening of the molecular weight distribution, whereby the polymers produced are more amenable to processing. This effect is also obtained, for example, in catalysts in which xcfx80I and xcfx80II are linked by a covalent bridge and a D/A bridge. The D/A xcfx80 structures according to the invention also enable polyethylene to be formed free from defects to an extent which is not possible with classical catalysts. Ethene polymers can accordingly be produced which have extraordinarily high melting temperatures which are higher than 135xc2x0 C. to 160xc2x0 C. for example (maximum of the DSC curve). Amongst these linear polyethylenes, those which are produced directly in the polymerisation process and which have melting temperatures of 140 to 160xc2x0 C. (maxima of the DSC curve), preferably 142 to 160xc2x0 C., most preferably 144 to 160xc2x0 C., are particularly important. This applies in particular to those which can be produced using the claimed xcfx80-complex compounds. Compared with known polyethylenes, new high-melting polyethylenes such as these have improved mechanical properties and resistance to thermal deformation (capacity for sterilisation in medical applications), and therefore open up possibilities for the use of polyethylenes which have hitherto appeared impossible and which could only be achieved hitherto, for example, by highly tactic polypropylene. Other features include high enthalpies of fusion and high PE molecular weights.
Over a wide temperature range, the molecular weight of the PE is in fact reduced by increasing the polymerisation temperature, but this occurs without any appreciable decrease in activity and without departing as a whole from the sphere of high PE molecular weights and high PE melting temperatures which are of interest commercially.
Furthermore, it has been observed that xcfx80-complex compounds of suitable symmetry according to the invention result in the regiospecific (isotactic, syndiotactic) polymerisation of suitable monomers, but in the upper part of said temperature range initiate what is an increasingly non-specific (atactic) linking of the monomer units for the same monomer. This phenomenon is not yet completely understood, but could be in agreement with the observation that coordinate bonds on which an ionic bond is superimposed, such as the donor-acceptor bonds in xcfx80-complex compounds according to the invention, exhibit an increasing extent of reversibility at elevated temperatures. Thus it has been observed during the copolymerisation of ethylene and propylene that when both comonomers are present in the same amount a copolymer with a high propylene content is formed at a low copolymerisation temperature, whilst the propylene content decreases with increasing polymerisation temperature until finally it is polymers which predominantly contain ethylene which are formed at high temperature. The reversible dissociation and association of the D/A structure and the rotation of the xcfx80 systems in relation to each other which thereby becomes possible can 
be schematically illustrated as follows:
Due to this change between a bridged and an unbridged catalyst structure, catalysts are available for the first time which are suitable for the production of stereospecific/aspecific ligand arrangements which change in a defined manner using one catalyst only under alternating conditions.
This temperature-dependent dynamic behaviour of the xcfx80-complex compounds or metallocene compounds according to the invention at different temperatures accordingly makes it possible to produce different stereo block copolymers, for instance those of the isotactic and atactic polypropylene (i-PP-a-PP)n type, which can be of different composition (a) with respect to the relative amounts of isotactic polypropylene (i-PP) and atactic polypropylene (a-PP) and (b) with respect to the block or sequence lengths.
Another valuable property of D/A xcfx80-complex compounds according to the invention is the possibility of self-activation and thus the possibility of dispensing with expensive co-catalysts, particularly in the case of dianionic 
derivatives. In this situation, in the opened form of the D/A xcfx80-complex compound, the acceptor atom A binds an X ligand,, for example one side of a dianion, with the formation of a zwitterionic xcfx80-complex structure and thus produces a positive charge on the transition metal, whilst the acceptor atom A assumes a negative charge. A self-activation process such as this can occur intramolecularly or intermolecularly. This can be illustrated by the example of the preferred linking of two X ligandis to a chelate ligand, namely that of the butadienediyl-derivative: 
The binding site between the transition metal M and the C atom, which is still bonded, of the butadienediyl dianion shown in the formula exemplified above is then the site for the insertion of an olefine for polymerisation.
Furthermore, the xcfx80-complex compounds or metallocene compounds according to the invention are suitable for the production both of thermoplastic and of elastomeric polymers by the various methods of production cited above, wherein both highly crystalline polymers with an optimised melting range and amorphous polymers with an optimised glass transition temperature can be obtained.